# Standard deviation

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## Standard deviation

The square root of the variance. A measure of dispersion of a set of data from its mean.
Copyright © 2012, Campbell R. Harvey. All Rights Reserved.

## Historical Volatility

A measure of a security's stability over a given period of time. While there are various ways to calculate it, the most common way is to compute the average deviation from the average price over the period of time one wishes to measure. The historical volatility is often compared to the implied volatility to determine if a security is overvalued or undervalued. Generally, securities with a higher historical volatility carry more risk. It is also called realized volatility or the standard deviation. See also: Volatility.
Farlex Financial Dictionary. © 2012 Farlex, Inc. All Rights Reserved

## standard deviation

A statistical measure of the variability of a distribution. An analyst may wish to calculate the standard deviation of historical returns on a stock or a portfolio as a measure of the investment's riskiness. The higher the standard deviation of an investment's returns, the greater the relative riskiness because of uncertainty in the amount of return. See also risk, variance.
Wall Street Words: An A to Z Guide to Investment Terms for Today's Investor by David L. Scott. Copyright © 2003 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved. All rights reserved.

## Standard deviation.

Standard deviation is a statistical measurement of how far a variable quantity, such as the price of a stock, moves above or below its average value. The wider the range, which means the greater the standard deviation, the riskier an investment is considered to be.

Some analysts use standard deviation to predict how a particular investment or portfolio will perform. They calculate the range of the investment's possible future performances based on a history of past performance, and then estimate the probability of meeting each performance level within that range.

Dictionary of Financial Terms. Copyright © 2008 Lightbulb Press, Inc. All Rights Reserved.
References in periodicals archive ?
sdx: Estimates of population standard deviation for independent variable
For ease of comparison, both [beta] and [beta]* estimates are scaled by the ratio between the population standard deviations of the factor and of the dependent variable.
The effect of skewness and kurtosis on the one-sample t test and the impact of knowledge of the population standard deviation. Journal of Statistical Computation and Simulation, 46, 79-90.
The t distribution is a family of pdfs whose shape depends upon [nu] (the Greek letter nu used to designate degrees of freedom) and not upon [sigma], the population standard deviation. This distribution is bell-shaped like the normal distribution but is not quite as peaked, thus it is fatter in the tails (figure 6.2).
Total of 108 patients were taken (54 patients in each group randomly allocated) by using WHO sample size calculator, taking level of significance 5%, power of test 90%, population standard deviation 127, test value of population mean 228, anticipated population mean 156.
If we know the population standard deviation, we may test the null hypothesis, [H.sub.o]: [mu] = [[mu].sub.o] against an alternative that is either one-sided ([H.sub.a]: [mu] > [[mu].sub.o] or [H.sub.a]: [mu] < [[mu].sub.o]) or two-sided ([H.sub.a]: [mu] [not equal to] [[mu].sub.o]).
The variable of interest and auxiliary variable wererepresentedthrough y and x with the population means Y and X, population standard deviations Sy and Sx, coefficient of variations Cy and Cx respectively.

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